Even though Cane didn't get all the things that he wanted to know from Mason, because he was way more ignorant than he thought him to be, at least, he could conclude one thing; his guess was right. All the horrendous events that happened ten years ago were all fabricated and the King was behind it.
And if King Aeon had gone all those extra lengths to get a hold of the two packs, the Howling Wolf pack and the Blue Moon pack, under his thumb then, he could do the same thing again now. Not to mention he got a suitable weapon to ruin Cane because of the incident between Ethan and the Crown Prince Alan.
It wouldn't take long before he reached the point where he needed to choose between letting Ethan go or rebelling against the King, between the two the latter being out of the options. His pack couldn't afford to go to another battle.